1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. The present invention relates to a process, a machine, manufacture, or a composition of matter. The present invention particularly relates to, for example, a semiconductor device, a display device, a liquid crystal display device, an electroluminescence (EL) display device, a light-emitting device, a lighting device, a memory device, or a processor, relates to a method for manufacturing a semiconductor film, a semiconductor device, a display device, a light-emitting device, a lighting device, a power storage device, a memory device, or a processor, or relates to a method for driving a semiconductor device, a display device, a light-emitting device, a lighting device, a power storage device, a memory device, or a processor. In particular, one embodiment of the present invention relates to, for example, a semiconductor device, a display device, a light-emitting device, a memory device, or a processor including a transistor, or a driving method thereof, or relates to, for example, an electronic device including the semiconductor device, the display device, the light-emitting device, the memory device, or the processor.
In this specification, the semiconductor device indicates all the devices that can function by utilizing semiconductor characteristics. A display device, a light-emitting device, an electro-optical device, a semiconductor circuit, an electronic device, and the like include a semiconductor device in some cases.
2. Description of the Related Art
Attention has been focused on a technique for forming a transistor using a semiconductor film which is formed on a substrate having an insulating surface. The transistor is applied to a wide range of semiconductor devices such as an integrated circuit and a display device.
As a semiconductor film of a transistor, an amorphous silicon film, a polycrystalline silicon film, an oxide semiconductor film, or the like is used depending on the purpose. For example, in the case of a transistor included in a large display device, it is preferable to use an oxide semiconductor film or an amorphous silicon film which can be formed using the established technique for forming a film on a large substrate. On the other hand, in the case of a transistor included in a high-performance display device where driver circuits are formed over the same substrate, it is preferable to use an oxide semiconductor film or a polycrystalline silicon film which can form a transistor having a high field-effect mobility.
In recent years, the resolution of a portable information terminal has been made higher, and the area per pixel has been decreasing. Owing to the decrease in pixel area, the proportion of a wiring, a transistor, and a capacitor in the pixel is increased. The use of a copper wiring having a low resistance is effective in reducing the area of the wiring, for example. The use of a polycrystalline silicon film or an oxide semiconductor film having high field effect mobility is effective in reducing the area of the transistor, for example.
Patent Document 1 discloses a display device including a transistor having an oxide semiconductor film and a capacitor having an oxide semiconductor film.